In a development physicists are calling "huge," "tantalizing" and "unexpected," researchers have measured a signal that could herald a new kind of particle or force of nature.

Yet the finding is not yet conclusive, and leaves many researchers skeptical.

The discovery comes from an atom smasher called the Tevatron at the
Fermilab physics laboratory in Batavia, Ill. Inside the accelerator
there, particles are ramped up to near the speed of light as they race
around a 4 mile (6.3 km) ring. When two particles collide, they
disintegrate into other exotic particles in a powerful outpouring of
energy. [Wacky Physics: The Coolest Little Particles in Nature]

Scientists analyzed thousands of these collisions, and found a
suspicious pattern in about 250 more cases than predicted. In these
instances, the products of the collision between a proton and its antimatter partner, the antiproton, were different than expected.